The present invention relates to a method for generating virtual three-dimensional space and particularly to a method for generating virtual three-dimensional space from rough three-dimensional structured data generated on the basis of two-dimensional space data of a residence map, or the like, for expressing the shape of a subject in polygonal pillars and detailed three-dimensional structured data interactively generated on the basis of detailed information of a design drawing, or the like, for expressing the shape of the subject in detail.
In a space information providing system such as a map/drawing information system, the retrieval of information pertinent to positions such as route guidance, facility management, etc. is required. Accordingly, it is effective to use a method for retrieving an object while walking through virtual three-dimensional space constructed on a computer on the basis of actual city space to thereby refer to pertinent information on the basis of links from the object. To achieve such a system, it is necessary to construct virtual three-dimensional space which reflects actual city space and which can be put into practical use. Roughly, there are two methods for constructing such virtual three-dimensional space. One is a method in which detailed three-dimensional structured data are generated interactively by use of a CAD tool, or the like.
The other is a method in which rough three-dimensional structured data for expressing a subject in polygonal pillars are generated automatically from two-dimensional map data, or the like, and from building floor number information, or the like, associated with respective two-dimensional figures. This method will be described below with reference to FIG. 3. Using two-dimensional space data 301 expressing vector information and attribute data 302 of building floor number, or the like, associated with the two-dimensional space data, the total height of each building is calculated on the assumption of the height per floor so that polygonal pillars each having upper and lower surfaces formed on the basis of a building frame are generated. Structured data 303 are rough three-dimensional structured data generated by this method automatically. Incidentally, this method is described in Japanese Patent Application 8-118661 which is not opened yet. A method similar to this method is disclosed in JP-A-4-149681. JP-A-4-149681 discloses the fact that all Z ordinates of constituent points of each map element are not held correspondingly to the constituent points but one Z ordinate value is extracted correspondingly to each map element and held as height information to thereby reduce the quantity of three-dimensional data, and the fact that three-dimensional map data are generated on the basis of a two-dimensional map data file for holding coordinate values of constituent points of each map element displayed on a map and the height of each building as a map element held in an attribute data file for holding attribute information pertinent to each map element displayed on a map.
There is however a problem that enormous time and labor is required in the method of interactively generating all structured data by use of a CAD tool, or the like, to construct virtual three-dimensional space. Although it is necessary that the quantity of data for virtual three-dimensional space is reduced as sufficiently as possible for the purpose of providing information through the Internet, this requirement cannot be satisfied if all structured data on the virtual three-dimensional space are interactively generated by use of a CAD tool, or the like.
On the other hand, according to the method in which rough three-dimensional structured data are generated automatically on the basis of two-dimensional map data, or the like, and on the basis of building floor number information, or the like, associated with respective two-dimensional figures, three-dimensional structured data can be generated from wide-range two-dimensional map data in a short time and on the basis of a smaller quantity of data. In this method, however, each building is often difficult to be understood as an object of navigation because all buildings are expressed in polygonal pillars.
To eliminate the difficulty of understanding each building as an object of navigation, therefore, it is thought of that only landmarks, or the like, allowed to be used as objects among the automatically generated rough structured data are selectively replaced by detailed structured data interactively generated by use of a CAD tool, or the like. FIG. 28 shows a flow of manual work for composing virtual three-dimensional space. In FIG. 28, the reference numeral 2801 designates virtual three-dimensional space expressed by rough three-dimensional structured data generated automatically; and 2802, detailed three-dimensional structured data generated interactively by use of a CAD tool, or the like. In a procedure 2803 for composing virtual three-dimensional space, the scale, parallel movement and rotation of the structured data are changed manually to thereby align rough three-dimensional structured data as a subject of replacement and detailed three-dimensional structured data to be substituted for the rough three-dimensional structured data. Thus, data on the automatically generated virtual three-dimensional space are partly replaced by detailed three-dimensional structured data. The reference numeral 2804 designates virtual three-dimensional space data composed in the aforementioned manner.
Much labor is, however, required for the alignment because a coordinate system for the detailed structured data generated interactively by use of a CAD tool, or the like, is not always accordant with a coordinate system for the rough virtual three-dimensional space generated automatically. Furthermore, because the flexibility in parallel movement, rotation, or the like, for the alignment in three-dimensional space is high, much manual work is required for composing virtual three-dimensional space from rough structured data and detailed structured data even in the case where only landmarks, or the like, allowed to be used as objects are selectively replaced by detailed structured data generated interactively by use of a CAD tool, or the like. Consequently, enormous labor is required.